This application is directed in general to diagnostic radiology using an X-ray device, system or apparatus. This application is directed in particular to an X-ray device, system or apparatus using a flat panel detector in a slot scanning configuration.
It is known that scattered X-rays have contrast reducing effects. One of the most significant challenges in using standard flat panel imaging is that, after performing X-ray imaging of an object (a patient for example), the X-ray image is composed of more scattered X-rays than direct transmitted X-rays, thus reducing contrast. This is especially true for thick objects (i.e., heavy patients).
Efforts have been made to improve contrast in diagnostic image radiology systems, including using air gaps, improved electronics and certain forms of scanning techniques. However, such known techniques have generally proved to be unsatisfactory in obtaining high image quality while maintaining rapid scanning rates and low exposure times. While it is possible to obtain images of good quality with very slow scanning speeds, as with a single scanning beam for example, such low speed scanning techniques are not practical in diagnostic radiology in view of the fact that the patients' body parts and organs move while the patients are being X-rayed. For example, it should be appreciated that the abdomen is the most difficult portion of the body to accurately X-ray in view of its relatively dense concentration of organs, bones and body fluids.
Thus, if relatively long exposure times are required to obtain an X-ray image, the images may be blurred due to the movement of the organs and body parts being X-rayed and are useless for diagnostic purposes. One possible solution is to use a post-patient collimator to reduce or eliminate scatter. One limitation associated with previously used post-patient collimators is that they do not totally reduce or eliminate scattered radiation and may block X-rays that have passed through the patient, forming useful doses.
Other efforts have been made to reduce or eliminate X-ray scattering, including using different types of slot scanners (pre-patient slot scanners for example) with an image detector, where the radiation is blocked prior to passing through the patient. In such manner, only slots of radiation are passed through to impinge on the patient. The detector and pre-patient collimator are swept across the patient, the images are collected and pasted together to form a single image. It is contemplated that this type of slot scanner configuration may result in a 4–10× dose reduction. Increasing the slots reduces the total scan time.
One example of a previous effort to reduce or eliminate X-ray scattering is disclosed in U.S. Pat. No. 4,096,391 (the '409 patent), incorporated herein by reference in its entirety, which discloses a slot scanner configuration using film (a film cassette for example). The '409 patent discloses a multiple slot scanning method and apparatus. A conventional X-ray tube projects a continuous X-ray beam in the direction of a patient. As described, a fore slot plate is positioned in the path of the X-ray beam at a predetermined position above the patient. The fore slot plate includes a plurality of narrow slots which permit the passage of a group of narrow parallel beam segments for scanning the patient.
Upon striking the patient, the narrow beam segments are partially defused or scattered in any a number of arbitrary directions. These scattered beam portions carry no significant information, and thus tend to blur or reduce the contrast in any resulting X-ray image. On the other hand, portions of the beam segments or portions penetrate directly through the patient. It is these penetrating beam portions which carry information as to the structural configuration of the patient's internal organs.
In the abdominal area for example, extremely clear, high quality X-ray images are necessary to obtain the degree of detail required to permit accurate diagnosis of disease or the detection of tumors and other improper growths. However, due to the thickness, dense concentration of material in the abdomen, and the large radiation field necessary to image the abdominal area, a large amount of X-ray scattering is created, thus making it difficult to obtain clear radiographic images of the abdomen, as mentioned previously. Accordingly, it is highly desirable and important to the advancement of abdominal diagnostic radiography for example, that clearer X-ray images of this area of the body be obtained.
It should be appreciated that such previously used slot scanners or pre-patient collimators have limitations. They require a fixed source to image distance (“SID”) (i.e., tube to detector). The materials used to detect the X-rays in the such previous designs (single crystal Si and Xe gas for example) do not work effectively for high kV imaging used for certain applications (radiography of R&F for example). Finally, the mechanical scanning used to form the image makes high frame rate imaging such as fluoro imaging difficult if not impossible.
One other known attempt to reduce or eliminate X-ray scattering includes using a slot scanner based on Xenon gas and avalanche detection. Still another attempt includes using a slot scanner based on single crystal Si sensors turned orthogonally to the X-ray incidence. While it is appreciated that both attempts may reduce X-ray scatter (due to the slot scanning) and photon counting, such attempts are generally only valid as scanned slot scanners.